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Want to Know How Your AC works?

Published on: July 31, 2012

It was an attempt to dehumidify the air of a printing plant that led to the world’s first electric-powered air conditioning system. In 1902, in order to make the plant’s indoor air dry enough so that the printed magazine pages would lie flat, American engineer Willis Carrier built an apparatus that pulled air over coils cooled with water. Carrier understood that cooled air would hold less moisture than warm air and would therefore help dehumidify the air. It wasn’t long before Carrier realized that people would pay to cool the air in their homes and businesses as well.

Carrier’s “Apparatus for Treating Air” was based on technology invented a half-century earlier to keep ice cold. It was discovered that certain liquefied gases cooled the air as they evaporated. Compressors were used to pump gases like ammonia and ether through condensers where the gases liquefied within a series of coils. The liquids were then pushed into an evaporator where the liquid vaporized into cooled gas. These early contraptions relied on water to cool the coils in the condenser, which meant that the machines needed access to plumbing to work.

In the 1930s, an air-cooled compressor was introduced. Soon after, window air conditioner units began to be manufactured. By the 1950s, sales for window air conditioners had passed one million. While air conditioning systems have been improved and refined over the last century, the basic principals behind the technology remain the same. The three main components of the HVAC system are still the compressor, the condenser and the evaporator, but refrigerants are what makes air conditioning technology possible.

Heat is needed to change the refrigerant liquid into a gas. As that transformation happens, the refrigerant pulls heat from the air, making the air feel cooler. Air conditioning HVAC systems use substances that can easily convert from a liquid to a gas and from a gas to a liquid. HVAC systems no longer use the toxic chemicals that early models used, and new chlorine-free refrigerants that won’t harm the ozone layer are becoming standard.

The three main components of a central air conditioning HVAC system do what their names describe. The compressor compresses refrigerant into a hot, pressurized gas and pumps the heated gas into a condenser. A fan blows air over the condenser, cooling the gas into a liquid. The condenser, which is made up of coils of tubing encased in a grid of metallic fins, condenses the liquefied gas under high pressure.

The cooled liquid enters the evaporator through an expansion valve that turns the liquid to a mist. The evaporator also has coils and metal fins to facilitate evaporation. As the liquid evaporates back into a gas, it cools the surrounding coils. A fan blows air across the evaporator and into the home. Gas from the evaporator is sent back to the compressor where the process begins all over again.

In a central air conditioning HVAC system, the cooled air flows through ducts into different rooms of the home. A thermostat placed in a central location measures the air temperature. When the set temperature is reached, the thermostat triggers the air conditioner to stop operation. When the temperature drops below the setting, the thermostat turns the air conditioner on again.

Air conditioning technology continues to advance and evolve, particularly in regard to energy efficiency. Today’s systems use around a third of the energy of models manufactured just 20 years ago. High efficiency compressors and improvements in fan blade shape and motors not only make systems more energy efficient but make them operate up to 20 times more quietly than older models as well. If your AC systems is older than seven years, you can enjoy significant reductions on monthly operating costs by installing a new AC system.